There are two major goals of this research. The first is to characterize the bipolar cell contribution to the primate flash electroretinogram (ERG) under both fully dark-adapted conditions, and in the presence of steady adapting backgrounds. The second goal is to use the isolated bipolar cell component to give us information about the role that bipolar cells play in visual signal processing. In order to obtain this understanding of bipolar cell responses, the technique of pharmacological isolation will be used in macaque monkeys, an animal whose retina is very close to that of man. An understanding of bipolar cell responses is important from both a clinical and a basic science point of view. At a basic level, bipolar cells clearly play an important role in retinal signal processing, and yet, because of the technical difficulties of recording form such cells in mammals, it has not been possible to carry out detailed studies of their response properties. Clinically, there are direct and indirect reasons for studying PH in the ERG. Directly, this information would be valuable in interpreting changes in the ERG that occur in diseases that involve bipolar cells themselves, such as congenital stationary night blindness. Indirectly, a good understanding of the characteristics of the PII component would allow better assessment of effects of retinal pathology on other components of the ERG, originating either distal to the bipolar cells (a-wave from photoreceptors affected, for example, by retinitis pigmentosa), or proximal to the bipolar cells (oscillatory potentials, scotopic threshold response from amacrine or ganglion cells affected, for example, by diabetic retinopathy, glaucoma or optic neuritis).